DOTS J. Francois
Internet-Draft Inria
Intended status: Standards Track A. Lahmadi
Expires: November 4, 2017 University of Lorraine - LORIA
M. Davids
G. Moura
SIDN Labs
May 3, 2017
IPv6 DOTS Signal Option
draft-francois-dots-ipv6-signal-option-02
Abstract
DOTS client signal using original signal communication channel can
expect service degradation and even service disruption as any other
service over Internet but in more severe conditions because the
signal may have to be transmitted over congested paths due to the
denial-of-service attack.
This document specifies a fall-back asynchronous mechanism using an
intermediate agent to store DOTS signal information during a limited
period of time. This mechanism allows a DOTS server to request a
signal information stored by a DOTS client when no heartbeat is
received from the DOTS client. This intermediate agent called DOTS
Signal Repository have to be connected to the DOTS client and server
independently. The repository must be located and/or reached through
one or multiple network paths, preferably as most as possible
disjoint from regular signal channel, in order to increase its
reachability. The document introduces a set of support protocols to
build the asynchronous communication between the DOTS cient, server
and the repository.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
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This Internet-Draft will expire on November 4, 2017.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Asynchronous DOTS signaling . . . . . . . . . . . . . . . . . 4
2.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Architecture . . . . . . . . . . . . . . . . . . . . . . 5
2.3. Asynchronous process . . . . . . . . . . . . . . . . . . 5
2.4. Protocol requirements . . . . . . . . . . . . . . . . . . 6
3. DOTS Signal Repository . . . . . . . . . . . . . . . . . . . 7
4. Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1. Between DSR and DOTS server . . . . . . . . . . . . . . . 7
4.2. Between DSR and DOTS client . . . . . . . . . . . . . . . 7
4.2.1. Opportunistic DOTS signaling . . . . . . . . . . . . 8
4.2.1.1. Hop-by-Hop option encoding . . . . . . . . . . . 9
4.2.1.2. DOTS signal Option attributes . . . . . . . . . . 10
4.2.1.3. Example . . . . . . . . . . . . . . . . . . . . . 11
4.2.1.4. Option Processing . . . . . . . . . . . . . . . . 12
4.2.1.5. Deployment considerations . . . . . . . . . . . . 14
4.2.1.6. Impact on existing IP layer implementations . . . 15
4.2.2. IPv6 SRH . . . . . . . . . . . . . . . . . . . . . . 15
5. Security Considerations . . . . . . . . . . . . . . . . . . . 15
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
8.1. Normative References . . . . . . . . . . . . . . . . . . 17
8.2. Informative References . . . . . . . . . . . . . . . . . 17
Appendix A. Additional Stuff . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
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1. Introduction
1.1. Overview
A distributed denial-of-service (DDoS) attack aims at rendering
machines or network resources unavailable. These attacks have grown
in frequency, intensity and target diversity
[I-D.ietf-dots-requirements]. Moreover, several protocols have been
utilized to amplify the intensity of the attacks [kuhrer2014exit],
peaking at several hundred gigabits per second.
DDoS Open Threat Signaling (DOTS) aims at defining a common and open
protocol to signal DDoS attacks to facilitate a coordinated response
to these attacks. This document specifies an asynchronous signaling
method that MAY be used between a DOTS client and server instead of
relying on purely synchronous communication as specified in
[I-D.ietf-dots-signal-channel]. Indeed initial signaling should be
done in real-time through connections between DOTS clients and severs
such that a client can forward signal information as soon as the
attack is detected. However, the signaling messages may have to be
forwarded through paths impacted by the attack itself, i.e. highly
congested. Asynchronous signaling in this document is an additional
mechanism which MAY propagate signal information in a less reactive
manner due to the use of an asynchronous communication channel but
through alternative paths in the network. It increases the
reachability of the DOTS server which will then in charge of
requesting the mitigation.
The proposed mechanism constitutes an additional signaling channel
but MUST NOT replace the original signaling channel used between DOTS
client and servers as the one defined in
[I-D.ietf-dots-signal-channel].
To perform asynchronous communication, this document introduces DOTS
Signals Repository (DSR) which represents datastores where DOTS
clients can send signal information. This information is then stored
and the DOTS server can request it. In addition to provide a general
process for achieving asynchronous signaling, this document
introduces also a set of protocols which can support it.
1.2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
The terms DOTS client, DOTS server, DOTS gateway, DOTS agents refers
to the terminology introduced in [I-D.ietf-dots-architecture].
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The following terms are introduced:
o DSR (DOTS signal repository): intermediate agent able to store
signal from clients during a limited period of time and which can
be requested by DOTS servers.
o Opportunistic DOTS signal: an IPv6 packet containing the signaling
attributes of an attack within the Hop-by-Hop extension header.
The purpose is the same as the DOTS signal. It is used to request
help for mitigating the attack.
o DOTS opportunistic-capable router: a router with the capacity to
decode the opportunistic DOTS signal and re-embed such an
information in other IPv6 packets.
o All DOTS opportunistic-capable agents are defined as the DOTS
agents supporting the opportunistic DOTS signal processing.
2. Asynchronous DOTS signaling
2.1. Motivation
The traffic generated by a DDoS can be characterized according to
various parameters, such as the layer (IP/ICMP or application),
maximum and instant throughput, among others. Regardless its nature,
we assume that for most cases, a DOTS client will be able to signal
back one or few messages, during the attack, to the DOTS phase.
We have the same behavior in other DDoS attacks. For instance, on
November 30th and December 1st, 2015, the Root DNS system was hit by
an application layer (DNS) attack [rootops-ddos]. Each one of the 13
root server letters (A-M) was hit by attacks peaking at 5 million
queries per second. By utilizing the RIPE Atlas DNSMON
infrastructure, we can see that during the DDoS attacks, most of the
root server letters remained reachable and able to respond to the DNS
request sent by the probes employed by the DNSMON [ripe-dnsmon-ddos].
Few letters, however, had a packet loss rate of more than 99%. The
DNSMON probes, however, experience mostly delays in their DNS
requests instead.
As regular signaling from the DOTS client to the DOTS server or the
DOTS gateway might be affected by the attack traffic, it is important
to maximize the delivering success of the signals by using
alternative packets and/or paths to deliver it. As a result, it
forces to have intermediate agents, DSRs, able to catch DOTS signals
delivered through those auxiliary mechanisms. However, those agents
MUST not always forward DOTS signal to the server in order to limit
the induced overhead. Only if the regular signal is not received by
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the server, retrieving the signal from the DSRs is required, which
has thus initiated by the DOTS server itself.
2.2. Architecture
DSR (DOTS Signal Repository) are additional REQUIRED datastores.
They are integrated in the DOTS architecture
[I-D.ietf-dots-architecture]as highlighted in Figure 1. (1) refers to
the regular signaling. (2) and (3) refers to the proposed auxiliary
mechanism. As shown in this figure, DSRs act as synchronizing agent
where the DOTS client drops signal information (2) (attack details).
On the contrary, the server will retrieve this information (3).
+-----------+ +-------------+
| Mitigator | ~~~~~~~~~~ | DOTS Server |~~~~+
+-----------+ +-------------+ |(3)
^ v
| +----------------+
(1)| | DOTS Signal |
| | Repository |
| +----------------+
| ^
+---------------+ +-------------+ |(2)
| Attack Target | ~~~~~~ | DOTS Client |~~~~+
+---------------+ +-------------+
Figure 1: Asynchronous signaling
2.3. Asynchronous process
This section describes the process of asynchronous DOTS signal
processing. In Figure Figure 1, there are two main communication
channels which are not synchronized:
o Between DOTS client and DSR: the client sends DOTS signal
information when a condition is satisfied. The condition MUST be
configured by the user but SHOULD be linked to information
provided by Attack target. For instance, when an attack is
detected, the client connects to DOTS server and in parallel sends
signal to one or more DSRs.
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o Between DOTS server and DSR: the server will retrieve signal
information when a specific condition occurs. Such a condition is
linked with the probable occurrence of an attack. The server can
infer this condition when the client is not responsive anymore.
In [I-D.ietf-dots-signal-channel], an heartbeat mechanism is
defined. Hence, when no heartbeat is received from the client,
the server MUST try to get signal information by the asynchronous
communication channel.
Each communication channel can implement its own protocol. They are
NOT REQUIRED to be the same.
We have to note that the client condition to provide signals to the
DSR can be weaker than regular synchronous signaling between DOTS
client and server. Indeed, a client can signal to the DSR some
suspect activities for which no mitigation is required yet. However,
when the supposed attack is stronger provoking client disruption, the
latter is not able to provide any type of signaling anymore and the
server can thus retrieve information on prior stored signals.
2.4. Protocol requirements
DOTS signaling requirements are documented in
[I-D.ietf-dots-requirements].
GEN-003 (Bidirectionality) requires that signal channel MUST enable
asynchronous communications between DOTS agent by allowing
unsolicited messages. Asynchronous signaling described in the
current document allows DOTS client to provide signals, which can be
retrieved later by DOTS server(s).
Because of this mechanism, there are requirements which are not
supported: OP-002 (Session Health Monitoring), OP-003 (Session
Redirection). Therefore, the fall-back asynchronous DOTS signaling
is an additionnal mechanism and MUST NOT replace regular signaling as
described in [I-D.ietf-dots-signal-channel].
It is particularly designed to fulfill GEN-002 (Resilience and
Robustness) by increasing the signal delivery success even under the
severely constrained network conditions imposed by particular attack
traffic.
In addition, the fall-back asynchronous DOTS signal MUST specify a
TTL (Time-to-Live) used by DSRs to store received signal in a limited
period of time. It is different from mitigation lifetime but MUST be
lower or equals.
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3. DOTS Signal Repository
DSRs have to be deployed and distributed in order to enhance its
reachability by the DOTS client. It is NOT REQUIRED that all DOTS
agents use the same set of DSRs and a DOTS client and server SHOULD
define their own set regarding their particular context, e.g. the
network topology. The Data channel [I-D.ietf-dots-data-channel]
between client and server MUST be used to configure it. As an
example in the case of the inter-domain scenario, the DOTS server can
inform the DOTS client to use DSRs scattered in multiple domains.
There is no restriction on the environment where DSRs can be
deployed. Two types of DSRs are mainly considered:
o Routers: they have low capacity to process and store received
signals but they are well distributed by nature in the network.
o Servers or stations: they provide higher computational power and
storage but are less distributed
Selection of protocols to use for asynchronous signaling MUST take
into account those specificities.
4. Protocol
4.1. Between DSR and DOTS server
To retrieve signals, the DOTS server MUST request the DSRs. Standard
protocols can be used. Requests from the DOTS server MUST specify a
client identifier and the DSRs returns all stored signal related to
this client. The protocol MUST provide integrity and authenticity
and SHOULD guarantee confidentiality. To limit entailed overhead
lightweight protocol SHOULD be used. COAP [RFC7252] over DTLS
[RFC6347] is RECOMMENDED when DSRs are servers. In the case of
routers acting as DSR, network management protocol such as SNMP
[RFC1157] or NETCONF [RFC6241] SHOULD be leveraged.
4.2. Between DSR and DOTS client
The signal sent by the DOTS client to the DSR is more prone to be
affected by attack traffic due to its proximity to the attack victim.
Similar protocol as between DSR and DOTS server can be used but it is
RECOMMENDED to convey the signal over multiple paths to increase the
reachability sucess
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This document introduces two mechanisms to deliver the signal from
the DOTS client to the DSR: IPv6 opportunistic signaling using Hop-
by-Hop Option header; source routing using IPv6 Segment Routing
Header (SRH).
4.2.1. Opportunistic DOTS signaling
This section specifies a signalling mechanism that instead of
designing a new application-layer protocol, it utilizes the IPv6 Hop-
by-Hop header [RFC2460]. This header SHOULD be processed by
intermediate devices and it MUST be the first header in IPv6
extension headers [RFC7045].
In such a particular scenario, DSRs are intermediate routers capable
of processing the option. DOTS server MAY also receive IPV6 packets
with the Hop-by-Hop option and could thus process it directly. It is
till considered as asynchronous since the server MAY NOT receive the
initial packet emitted by the client but a copy of the signal in
another packet (done by an intermediate DSR/router). Otherwise, it
MUST connect to the DSR (section Section 4.1)
The new option containing the attributes of the signalling message is
included in an opportunistic way in available IPv6 packets leaving a
network element. The DOTS client will thus embed the signalling
attributes into outgoing IPv6 packets not necessarily going to the
DOTS server. Intermediate routers receiving such a packet will
examine it and embed the same information into other IPv6 packets.
domain in this opportunistic way to increase the probability that
such a packet will be finally forwarded to a DOTS gateway or Server,
but also in controlled way to avoid that the mechanism is exploited
for a malicious purposes.
Only the Hop-by-Hop options header allows such behavior and using
Destination options header is not enough to make the DOTS signal
going through the network in an opportunistic way. Each network
element recognizing this new option will select the best fitted IPv6
packets to deliver the signal to the DOTS DSRs. For this reason the
Hop-by-Hop header option is essential to make such behavior compared
to other existing IPv6 extension headers [RFC6564].
The goal is to provide an efficient mechanism where nodes in a IPv6
network facing a DDoS attack can deliver a DOTS signal message sent
by a DOTS client to the DOTS server. The specified mechanism does
not generate transport packets to carry the DOST signal message but
it only relies on existing IPv6 packets in the network to include
inside them a hop-by-hop extension header which contains an encoded
DOTS signal message. The solution defines a new IPv6 Hop-by-Hop
header option with the semantic that the network node SHOULD include
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the option content within one or multiple outgoing IPv6 packets
available in that network node.
4.2.1.1. Hop-by-Hop option encoding
According to [RFC2460], options encoded into the IPv6 Hop-by-Hop
header are formatted as Type-Length-Values (TLVs). The option for
opportunistic DOTS signal is thus defined as described in Figure 2
0 7 15 22 31
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option type |Option Data Len| DOTS Signal Attribute[1] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DOTS Signal Attribute[2] | ... | DOTS Signal Attribute[n] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Hop-by-Hop option encoding
The first byte defines the Hop-by-Hop Option type number allocated to
the DOTS opportunistic signalling. This number is not yet fixed but
the first three bits MUST be set to 0. The first two zero bits
indicate that routers which cannot handle the DOTS signal option will
continue to process other options. The third 0 bit means that the
option processing will not change the packet's final destination
[RFC2460].
The second byte contains the length of the option content. The
content of the DOTS Signal option is a variable-length field that
contains one or more type-length-values (TLV) encoded DOTS signal
attributes, and has the format described in Figure 3.
0 7 15
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attr Type | Attr Data Len | Attr Data ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Hop-by-Hop option encoding
The Attr Type is 8-bit identifier of a DOTS signal attribute.
The Attr Data Len is 8-bit unsigned integer which is the length of
Attr Data in bytes.
The Attr Data is variable-length field that contains the data of the
attribute.
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Since using TLVs in Hop-by-Hop options is known to be a factor of
attacks [I-D.krishnan-ipv6-hopbyhop], DOTS attributes are encoded
with fixed length when possible.
4.2.1.2. DOTS signal Option attributes
The first attribute embedded into the opportunistic DOTS signal is a
TTL (Time-to-Live) field which indicates the maximum number of
retransmission of the signal into another IPv6 packets until it MUST
be discarded. Remaining attributes are similar to the header fields
described in [I-D.ietf-dots-signal-channel] used to convey a DOTS
signal through a HTTP POST.
The sequence of attributes to be inserted within the header MUST
start with fixed-length attributes which are defined in the following
order:
o TTL: Time-to-Live. This is a mandatory attribute encoded in one
byte.
o Flags: one byte is reserved for flags.
The first bit indicates the type of the IP address of the host: 0
for IPv4, 1 for IPv6. The second bit indicate if the protocol to
use is TCP (1) or UDP (0). The third bit indicates if the message
is signed. The remaining bit are not used yet.
o host: the IP address of the DOTS server where the signal option
SHOULD be delivered. Depending on the flags, this field is
encoded in 4 or 16 bytes.
o port: the listening port of the DOTS server. It is encoded in 2
bytes.
The remaining attributes MUST be TLV encoded, and they are defined in
the following order:
o policy-id: defined in [I-D.ietf-dots-signal-channel].
o target-ip: defined in [I-D.ietf-dots-signal-channel].
However, each address or prefix is encoded in its own TLV element.
The distinction between IPv4 and IPv6 is done over the length of
the value.
o target-port: defined in [I-D.ietf-dots-signal-channel].
However, each target port is encoded in its own TLV element.
o target-protocol: defined in [I-D.ietf-dots-signal-channel]
However each target protocol is encoded in its own TLV element.
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o lifetime (lt): lifetime of the mitigation request defined in
[I-D.ietf-dots-signal-channel]
The encoded attributes MUST be included in the option header in the
order defined above.
Table 1 provides the value of types that are used by the TLV encoded
attributes.
+-----------------+-------+
| Attribute type | Value |
+-----------------+-------+
| policy-id | 0 |
| target-ip | 1 |
| target-port | 2 |
| target-protocol | 3 |
| lifetime | 4 |
+-----------------+-------+
Table 1: TLV encoded attributes types
4.2.1.3. Example
Following is an example of an encoded Hop-by-Hop Option header to
signal that a web service is under attack.
0 7 15 22 31
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next header | Hdr Ext Len=6 | TTL=128 | Flags=IPv4,TCP|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| host=192.0.2.1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| port=443 | A. type=policy| Att Data Len=2|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 143 | Attr. type=ip| Att Data Len=4|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 192.0.2.20 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attr. type=ip |Att Data Len=16| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
+ +
| |
+ +
| 2001:db8:6401::1 |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Attr. type=port| Att Data Len=2|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| 8080 |Attr. type=port| Att Data Len=2|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 443 |Attr.type=proto| Att Data Len=2|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TCP | Attr. type=lt | Att Data Len=2|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 600 | 1 | Opt Data Len=0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Example of Hop-by-Hop DOTS signal encoding
In the previous example, the message is not signed and terminates
with padding. If it is the case, then the signature MUST BE added at
the end such that the integrity and authenticity can be checked by
the DOTS server or gateway. The TTL attributes MUST be excluded from
the signature calculation.
4.2.1.4. Option Processing
4.2.1.4.1. Opportunistic DOTS signal initialization by a DOTS client
When a DOTS client needs to inform the DOTS server that it is under
attack, it firstly makes a connection attempt and applies the
mechanisms described in [I-D.ietf-dots-signal-channel].
In addition, it MAY activates an opportunistic mechanism to include
the Hop-by-Hop header option specified in this document in one or
multiple available IPv6 packets leaving the node. Because the DOTS
client location is independent of the signalling, it can be
positionned in a part of the network where there is no passing-by
traffic which can serve for opportunistic signalling. DOTS client
MAY also create and emit IPv6 datagrams without payload but with the
signal encoded in the Hop-by-Hop option header.
Otherwise, the selection of packets has to be configured a priori.
The configuration is composed of a sequence of rules defined in a
hierarchical order such that they are triggered in a sequential
manner.
The selection of packets has to be configured a priori. The
configuration is composed of a sequence of rules defined in a
hierarchical order such that they are triggered in a sequential
manner.
Each rule is defined by:
o a set of filters over the IPv6 packet headers. Only packets
matching those filters are selected for opportunistic signalling.
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For instance, only packets heading to a given subnetwork or to
specific address close to a DOTS server can be selected to
increase the chance to reach the latter.
o a ratio to select only a proportion of packets matching the
filters in order to limit the induced overhead of the
opportunistic signalling.
o a timeout until the rule is active and selected IPv6 packets embed
the DOTS opportunistic signal.
The objective is to apply each ordered rule after another according
to their timeouts. The first rule is triggered immediately after the
opportunistic signalling is activated.
In all cases (embedding information into an exsiting packet or
creating an new pakket with no payload), the client MUST avoid
fragmentation.
Although the definition of rules MUST be configured by the user. It
is RECOMMENDED to order them inversely related to the number of
packets that would be selected. This can be approximated regarding
the definition of filters. The core idea is to benefit from the
first instants of the attack before losing connectivity by using a
maximum number of outgoing packets to include the DOTS signalling
option. It is thus RECOMMENDED to define the first as matching all
IPv6 packets with a ratio equals one to rapidly disseminate the
information but with a short timeout to limit the implied overhead.
Here is the an example of rules:
1. all outgoing IPv6 packets with a 10 second timeout
2. all outgoing IPv6 packets with a ratio of 10% and a 1 minute
timeout
3. all outgoing multicast IPv6 packets with a ratio of 10% and a 1
minute timeout
4. all outgoing IPv6 packets heading to the DOTS server with a ratio
of 100% and a one hour timeout
4.2.1.4.2. Processing by a non DOTS opportunistic-capable router
When receiving an opportunistic DOTS signal encoded in a IPv6 packet,
a non DOT opportunistic capable router simply skips the Hop-by-Hop
option and continue the normal processing of the IPv6 packet because
the option type MUST start with three zero bits.
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4.2.1.4.3. Processing by a DOTS opportunistic-capable router
A DOTS opportunistic-capable router MUST store DOTS signalling
information whose it is aware of. If a router processes an IPv6 DOTS
opportunistic signal and supports this option, it first checks if it
has already stored the associated information. In that case, the
router simply skips the option and continues the normal processing
otherwise it stores the encoded information in order to embed it
again in other IPv6 packets similarly to the DOTS client. Hence, a
set of rules are also defined in advance and are triggered upon the
reception of a new opportunistic DOTS signal. Once all rule have
been applied, signalling information MUST be discarded by the router.
When embedding the information into other IPv6 packets, the router
MUST decrease the TTL by one since opportunistic signalling does not
prevent loops in the dissemination of signalling.
4.2.1.4.4. Processing by a DOTS opportunistic-capable gateway
If a DOTS gateway has DOTS capabilities, it will apply the same
strategy as a DOTS client by making attempts of direct connections to
the DOST server and in addition it inserts the Hop-by-Hop header DOTS
signalling option in leaving IPv6 packets using the strategy
specified above.
4.2.1.4.5. Processing by a DOTS opportunistic-capable server
When the IP layer of the host where the DOTS server is running
receives an IPv6 packet carrying a Hop-by-Hop DOTS signal option
header it MUST extracts the content of the option and provides the
attributes data to the server program.
4.2.1.5. Deployment considerations
This mechanism will be potentially used by networks with IPv6 capable
elements and requires that of IPv6 traffic exist in the network
during the attack. The existing IPv6 traffic to be used could be of
any type from management or user levels. It is also important to
emphasize that while our mechanism utilizes an IPv6 header field, it
can also be used to signal IPv4 attacks as well - given that the
network devices are dual stacked.
IPv6 extension headers are often rate-limited or dropped entirely.
To be able to use the mechanism specified in this document, network
operators need to avoid discarding packets or ignoring the processing
of the hop-by-hop option on their deployed network elements.
However, instead of dropping or ignoring packets with hop-by-hop
option carrying DOTS signal, they need to assign these packets to
slow forwarding path, and be processed by the router's CPU. This
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behavior will not affect the performance of the network devices since
the network is already facing a DDoS attack and fast forwarding paths
are saturated by the attacker traffic.
If the DOTS server, gateway and the client are located in the same
administrative domain, marking the IPv6 packets with the proposed
hop-by-hop header option could be done in a straight forward way,
while considering that an agreement exists inside the domain to avoid
dropping or rate limiting of IPv6 extension headers as described
above. The proposed mechanism becomes less practical and difficult
to deploy when the DOST server is running on the Internet. In such
scenario, the mechanism could be used in the intra-domain part to
deliver the hop-by-hop option carrying the DOTS signal until it
reaches a DOTS gateway located in the same domain as the client, then
the gateway will apply mechanisms provided by the DOTS transport
protocol [I-D.ietf-dots-signal-channel] to inform the server running
on Internet about the attack. This deployment scenario requires that
at least one DOTS gateway is deployed in the same domain than the
DOTS client.
4.2.1.6. Impact on existing IP layer implementations
For this option to be applicable within an IP system, it requires
modifications to existing IP layer implementation. At DOTS capable
nodes (client, gateway and server), it requires a service interface
used by upper-layer protocols and application programs to ask the IP
layer to insert and listen to the Hop-by-Hop header option in IPv6
packets. A DOTS client invokes the service interface to insert the
option, A DOTS gateway invokes the service interface for listening
and inserting the option, and finally a DOTS server only invokes the
service interface to listen to the DOTS signalling option.
Intermediate nodes (routers or middle boxes) IP layer needs to be
extended to perform processing of the new Hop-by-Hop header option.
They mainly parse the first host attribute of the option and make a
selection of a leaving IPv6 packet where the option will be inserted.
Every node inserting the new proposed Hop-by-Hop option SHOULD only
select IPv6 packets with enough left space to avoid fragmentation.
4.2.2. IPv6 SRH
DOTS signalling may be carried using IPv6 source routing header.
Details will be provided in a later version of this document.
5. Security Considerations
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Any IPv6 header option could be used by an attacker to create an
attack on the routers and intermediate boxes that process packets
containing the option. The proposed IPv6 option in this document MAY
be abused by an attacker to create a covert channel at the IP layer
where data is hidden inside the content of the option [RFC6564].
However, this attack is not specific to the proposed option and it is
a known issue of IPv6 header extensions and options. The option MAY
also be used by an attacker to forge or modify opportunistic DOTS
signal leading to trigger additional processing on intermediate nodes
and DOTS servers.
However the proposed option should be only initiated by a DOTS client
and information embedded in new IPv6 messages by opportunistic DOTS
capable routers. Defining proper policies to filter all messages
with this option set and originated from other nodes would limit
security issues since these DOTS opportunistic-capable agents SHOULD
be trustworhy.
In addition, the message MAY be signed using techniques to enforce
authenticity and integrity over the opportunistic DOTS signal
channel. The signalling message specification includes a flag to
indicate if the message is signed by the choice of the signature
algorithm is let to the users. This signature has to be computed by
the DOTS opportunistic-capable client and checked by the DOTS
opportunistic-capable gateway or router. Hence, intermediate routers
MUST NOT modify the message and its signature except the TTL, which
so has not be considered during the signature computation.
Assuming a compromised router, the attacker could nevertheless replay
the message or increase the TTL but thanks to the unique policy-id
all intermediate-DOTS capable router will drop such messages and thus
limiting their forwarding in the network.
Besides, an attacker can also listen opportunistic DOTS signals to
monitor the impact of its own attack. These considerations are not
specific to the proposed option and supposes that the attacker is
able to compromise intermediate routers.
6. IANA Considerations
This draft defines a new IPv6 hop-by-hop option[RFC2460].This
requires an IANA RFC3692-style update of:http://www.iana.org/
assignments/ipv6-parameters/ipv6-parameters.xhtml and ultimately the
assignment of a new hop-by-hop option according to the guidelines
described in [RFC5237].
7. Acknowledgements
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This work is partly funded by FLAMINGO, a Network of Excellence
Seventh Framework Programme.
8. References
8.1. Normative References
[I-D.ietf-dots-architecture]
Mortensen, A., Andreasen, F., Reddy, T.,
christopher_gray3@cable.comcast.com, c., Compton, R., and
N. Teague, "Distributed-Denial-of-Service Open Threat
Signaling (DOTS) Architecture", draft-ietf-dots-
architecture-01 (work in progress), October 2016.
[I-D.ietf-dots-data-channel]
Reddy, T., Boucadair, M., Nishizuka, K., Xia, L., Patil,
P., Mortensen, A., and N. Teague, "Distributed Denial-of-
Service Open Threat Signaling (DOTS) Data Channel", draft-
ietf-dots-data-channel-00 (work in progress), April 2017.
[I-D.ietf-dots-requirements]
Mortensen, A., Moskowitz, R., and T. Reddy, "Distributed
Denial of Service (DDoS) Open Threat Signaling
Requirements", draft-ietf-dots-requirements-04 (work in
progress), March 2017.
[I-D.ietf-dots-signal-channel]
Reddy, T., Boucadair, M., Patil, P., Mortensen, A., and N.
Teague, "Distributed Denial-of-Service Open Threat
Signaling (DOTS) Signal Channel", draft-ietf-dots-signal-
channel-01 (work in progress), April 2017.
[I-D.krishnan-ipv6-hopbyhop]
Krishnan, S., "The case against Hop-by-Hop options",
draft-krishnan-ipv6-hopbyhop-05 (work in progress),
October 2010.
8.2. Informative References
[RFC1157] Case, J., Fedor, M., Schoffstall, M., and J. Davin,
"Simple Network Management Protocol (SNMP)", RFC 1157, DOI
10.17487/RFC1157, May 1990,
.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997,
.
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[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, .
[RFC5237] Arkko, J. and S. Bradner, "IANA Allocation Guidelines for
the Protocol Field", BCP 37, RFC 5237, DOI 10.17487/
RFC5237, February 2008,
.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, .
[RFC6564] Krishnan, S., Woodyatt, J., Kline, E., Hoagland, J., and
M. Bhatia, "A Uniform Format for IPv6 Extension Headers",
RFC 6564, DOI 10.17487/RFC6564, April 2012,
.
[RFC7045] Carpenter, B. and S. Jiang, "Transmission and Processing
of IPv6 Extension Headers", RFC 7045, DOI 10.17487/
RFC7045, December 2013,
.
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252, DOI 10.17487/
RFC7252, June 2014,
.
[kuhrer2014exit]
M. Kuhrer, T. Hupperich, C. Rossow, T. Holz, "Exit from
Hell? Reducing the Impact of Amplification DDoS Attacks",
USENIX Security Symposium 23rd, 2014.
[ripe-dnsmon-ddos]
RIPE, "NCC DNS Monitoring Service (DNSMON)", .
[rootops-ddos]
rootops., "Events of 2015-11-30", 2015,
.
Appendix A. Additional Stuff
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This becomes an Appendix.
Authors' Addresses
Jerome Francois
Inria
615 rue du jardin botanique
Villers-les-Nancy 54600
FR
Phone: +33 3 83 59 30 66
Email: jerome.francois@inria.fr
Abdelkader Lahmadi
University of Lorraine - LORIA
615 rue du jardin botanique
Villers-les-Nancy 54600
FR
Phone: +33 3 83 59 30 00
Email: Abdelkader.Lahmadi@loria.fr
Marco Davids
SIDN Labs
Meander 501
Arnhem 6825 MD
NL
Email: marco.davids@sidn.nl
Giovane Moura
SIDN Labs
Meander 501
Arnhem 6825 MD
NL
Email: marco.davids@sidn.nl
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